<html>
    <head>
        <script src="jquery-3.3.1.js" type="text/javascript"></script>
        <script>
            $(function(){ 
            var div2 = document.getElementById("div1");
            console.log(div2);
                var div1 = $("#div1");
            console.log(div1);
            console.log(div1[0]);//jq转换成js
            console.log($(div2));//js转换成jq
             $("#btn1").click(function(){
                 alert(123);
             })
             $("#btn1").mouseout(function(){
                 alert(456);
             })
             $("#btn2").click(function(){
             $("#btn1").off("mouseout");
             })
             
            })
            
            $(function(){
                console.log("1111")
                $("#div2").css("background-color","red");
            });
        </script>
        <body>
            <div id="div1">123</div>
            <div id="div2">456</div>
            <div id="div3">789</div>
            <input type="button" value="按钮" id="btn1">
            <input type="button" value="解绑按钮" id="btn2">
        </body>
    </head>
</html>